Review of Primer Types for Automotive Use
The first step to a durable, long lasting automotive finish is choosing the correct primer for your paint job’s foundation. With so many primer options available it’s often confusing which primer system is best suited for your restoration project. Here is a quick overview of the common types used in restoration and repair in restoration shops around the world.
A good two part epoxy primer is your best choice for bare metal to provide excellent adhesion and corrosion resistance long term. However, when formulated for best corrosion resistance epoxies typically do not sand well when compared to urethane primer surfacers.
Urethane Primer Surfacer
Two part urethane primer surfacers, or primer filler, as they are sometimes called fills and sands better than epoxy but does not have as good of corrosion resistance/adhesion to bare metals as epoxy therefore they are often used over epoxy primer and/or putty and filler materials to provide the best performance as a system.
Polyester Primer Surfacer
Excellent build when you can’t always get your body work as well as you would like. However, polyester surface is often more brittle and prone to crack over time than polyurethane surfacers. Generally the highest filling capability of any sprayable primer type.
Urethane sealers are not the best choice for filling, sanding, or direct to bare metals but do provide a nice foundation for applying topcoat color over if the item you are painting is already in good shape or you have a lot of filler primer and bodywork to seal off. Often available in bright colors to help with coverage on more transparent color like bright yellows, and reds.
Acid Etch Primer
Etch primers provide good direct to metal adhesion and corrosion but generally not as good as corrosion resistance as epoxy primer. However, etch primer is faster than epoxy so it is frequently used in collision repair to improve through put. Epoxy primer is used more often on bare metals than etch primer in restoration work.
Lacquer Primer is great for speed and sanding but not so good for long term durability. Shrinkage, cracking, and bubbling are common long term problems associated with lacquer primer.
Enamel primers are economical and provide fair sealing/corrosion resistance but can be susceptible to lifting/wrinkling with some systems.
Moisture Cure Urethane
Moisture Cure urethane primers are great for adhesion and rust protection on pitted metals where rust can not be completely removed. These primers cure on exposure to atmospheric moisture.
If you have specific questions about any restoration project feel free to drop us a line at email@example.com. We’d be happy to help.